1. Field of the Invention
The invention relates to waveform display apparatus in the nature of a digital storage oscilloscope and, in particular, to automotive engine analyzers which utilize such a digital oscilloscope as a display screen.
2. Description of the Prior Art
It is known to provide engine analyzers with screen displays which essentially constitute digital oscilloscopes. In particular it is known to provide dual-trace digital oscilloscope displays in digital engine analyzers for the purpose of analyzing multi-cylinder internal combustion engines of vehicles. Two of the engine waveforms which are commonly displayed on an engine analyzer scope are the primary and secondary ignition voltages which appear, respectively, across the primary and secondary windings of the ignition coil. The primary and secondary waveforms are typically acquired from the engine by means of separate primary and secondary pickup leads. The analyzer also typically has a no. 1 cylinder lead to detect the firing of the no. 1 cylinder, so that the analyzer can identify the cylinders once the firing order of the engine is known. Other leads may be utilized to acquire other types of waveforms generated by the engine. The acquired waveforms are processed, digitized and stored in memory for display on the oscilloscope, in either live or freeze mode.
In addition to displaying actual engine waveforms on the oscilloscope, an engine analyzer can also perform various diagnostic tests on the input signals and generate various types of screen displays of the test results. One such digital engine analyzer is disclosed, for example, in U.S. Pat. No. 5,250,935 to Jonker et al. That analyzer is provided with a user interface in the form of a keyboard including function keys with screen-defined functions for inputting to the system pertinent information regarding the vehicle and/or engine under test and test selection options.
Analysis of the engine-generated signals may also include comparison of the input signals with known or standard criteria or specifications for properly operating engines. For this purpose, some engine analyzers store data bases including pertinent information regarding the vehicle under test. This information may include, for example, the identification of the vehicle, the particular type of engine, as well as selected specifications of the engine. One such analyzer is disclosed in U.S. Pat. No. 4,128,005, and generates diagnostic signals representing the relationship between engine operating parameters and engine specifications. Diagnostic signals are selectively processed according to a test matrix to determine the operating state of each engine component. The diagnostic message then identifies which, if any of the components requires repair or replacement. However, that system simply compares parameter values relative to the engine under test with stored engine specifications, and does not involve analysis of waveform information.
It is also known to provide an engine analyzer with a data base of reference information which includes a library of signal waveform patterns, which may include generic standard or reference patterns, known "good" patterns for a properly operating engine, or known "bad" patterns which typify known specific trouble conditions. In order to compare an input signal waveform pattern with one of the library patterns, the user has had to scroll through the entire library of patterns or, at least, a list of all the patterns in the library to select the pattern or patterns which are most appropriate for the comparison which he wishes to perform. This can be quite time consuming.